Thermionic regulator



June 19, 1923.

P. WOLD THERMIONIC REGULATOR Filed July 29, 1918 Patented June 1 9,1923.

UNITED STATES PATENT OFFICE.

PETER IRVING WOLD, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELEC-TRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEWYORK.

THERMIONIC REGULATOR.

Application filed July 29, 1918.

1 "0 all who m. it may concern:

Be it known that I, Pn'rnn IRVING won), a citizen of the United States,residing at East. Orange, in the county of Esex and State of N cwJersey, have invented certain new and useful Improvements in ThermionicRegulators, of which the following is a full, clear, concise, and exactdescription.

This invention relates to a novel type of regulator which is applicablein general for the regulation of electric currents and is particularlyadapted to be employed for regulating the electrical output such as thevoltage or current of a generator, or for controlling the electricalenergy applied to a motor in order that its speed may be regulated.

An object of this invention is to produce a regulator for electricgenerators which will maintain a constant voltage or a constant currentoutput. Another object is to produce such a regulator as will becontinuously acting and in which there will be no moving parts such asare present in relays and the like. Still another object is to provide aregulator that is light in weight and which may be readily employed as aregulator for an electric machine without the necessity of altering theconstruction of the machine.

The regulator provided according to the present invention is of thethermionic typ: such as an audion comprising a vacuum tu containingelectrodes. The manner in which such a vacuum tube is employed as aregulator is this: The vacuum tube comprises a. cathode which serves asa source of electrons that travel to the anode or plate electrode. Theamount of this electron stream or space current depends upon severalfactors, primarily upon (a) the voltage applied between theseelectrodes; (1)) the temperature of the cathode, an increase intemperature producing a stronger space current; and (0) the potential ofthe grid electrode with respect to the filament, the more positive thepotential of the grid within certain limits, the greater will be thespace current.

An important feature of this invention is that such a vacuum tube asabove described is an amplifier, that is, the application of a givenvoltage on the grid is more efi'ective in controlling the impedance ofthe tube as measured between the cathode and anode Serial No. 247,275.

electrodes than the application of the same voltage applied between thetwo last mentioned electrodes. On account of its amplitying properties avacuum tube of the threeelectrode type is therefore well adapted toregulate the current or voltage of a circuit with great sensitiveness.

If it is desired to regulate the output of the generator in accordancewith this invention, the field winding thereof may be connected incircuit with the cathode and plate electrodes. The output of thegenerator depends of course upon the field current which, within limits,is controlled by the current flowing between the cathode and plateelectrodes and which may be varied in intensit by varying the potentialapp-lied to the sici. The increase in the voltage or current of thegenerator serves to vary the potential of the grid, thereby modifyingthe space current so that the desired regulation is obtained.Specifically, the vacuum tube is connected in shunt to the field windingof the machine, and the field current is variably diverted through thevacuum tube in accordance with the potential of the grid electrode whichis responsive to the voltage or current to be regulated.

As the thermionic device may be associated with, an electric machine ina variety of ways, several forms that this invention may possess arehereinafter described in detail in connection with the drawings, inwhich Fig. 1 represents an embodiment of this invention in connectionwith a shuntwound direct current generator for voltage regulation, whileFig. 2 shows the invention adapted to regulate for constant current.Fig. 3 illustratesa thermionic regulator in connection with theseries-wound generator.

Referring more particularly to Fig. 1, 7 is a direct current generatorhaving a field winding 8. In series With the field winding is anadjustable resistance 9. In shunt with this winding is a high resistance10 and also the anode 11 and cathode 12 of a vacuum tube amplifier 13.The grid 14 of the tube is connected to an intermediate point of theresistance 10 by tap 15. The grid 14 is therefore positive with respectto the oath ode 12 by the I R drop across that part of resistance 10which is included between tap 15 and the cathode. With such anarrangement the vacuum tube 13 serves as a shunt path across theterminals of field winding 8, and since the potential of the griddetermines the value of the impedance of the tube, it follows that thepotential of the grid determines the value of the field winding current.If, now, the voltage of the generator 7 should tend to increase, due,for example, to a change in the speed of the generator or a change inits load, the I R drop across resistance 10 would become larger, therebymaking the grid more positive with respect to the filament, increasingthe current through the vacuum tube and making it a more complete shuntfor the field winding 8. The current through the field winding wouldtherefore decrease, thereby reducing the voltage of the generator andsubstantially annulling the change in its output voltage across theleads 18, 19 of the generator. In a similar manner, it the voltage ofthe generator would tend to decrease below the desired value, the gridwould become less positive, thereby decreasing the current flowing inthe tube and consequently increas ing the current flowing through thefield winding so that voltage of the generator would be heldsubstantially constant.

Fig. 2 shows how a thermionic regulator 20 may be employed to regulate adirect current generator 21 for constant current output. As in Fig. 1,the anode 22 and cathode 23 of the thermionic regulator 20 are shuntedacross the terminals of the field winding 25. The anode and cathode areso connected in the circuit of the generator that the anode is madepositive with respect to the cathode. Included between the negativeterminal of the generator and the line 18 is a resistance 26 which is soconnected in circuit with the cathode 23 and grid 27 that the I R dropacross its terminals tends to make the grid positive with respect to thecathode. Since the resistance 28, which is in series with the fieldwinding 25, is also connected between the cathode and grid of the tube,it follows that the resultant potential of the grid is determined by thealgebraic sum of the I R drop in resistance 28 and the I R drop inresistance 26. It is preferable, however, that the values of these resistances should be so adjusted that the resultant potential of the grid27 is positive with respect to the potential of the cathode 23. Ifdesired, the resistance 28 may be connected between the other end ofcoil 25 and the positive terminal of the generator 21, in which case itwill still be effective in adjusting the field current, but will not bea part of the grid circuit, and in this case the potential of grid 27will depend on the I R drop through 26 only. Since resistance 26 is inseries with lead 18 with respect to the generator 21, the potential ofthe grid is dependent upon the current supplied to the line 18 and willvary as the current varies.

The thermionic regulator will therefore regulate for constant current,for if the current of the generator would tend to increase, due forexample, to an increase in the speed of the generator or a decrease inits load, the I R drop in resistance 26 would become greater, therebymaking the grid more posi tive, decreasing the impedance of the tube 20and causing a corresponding decrease in the field winding current. Thischange in the field winding current would consequently tend to reduce toa low value the change in the output current of the generator. In asimilar manner, it the current output of the generator would tend todecrease, thereby making the grid less positive, the impedance of thetube would increase and the field winding current would increase so thatthe desired regulation would be obtained.

Although 26 is shown as a resistance its important function is to give asource of potential connected to the grid which shall be responsive orproportional to the current flowing through the load. As such it may bethe resistance in the series coil of a compound wound machine, in .whichcase it will serve the purpose of doubly correcting for fluctuationsfirst by its ampere turns on the field itself and second by controllingthe impedance of the vacuum tube.

Fig. 3 shows this invention adapted to regulate a series-woundgeneratorfor constant voltage output. 35 is a generator having a series winding36 and leads 37 and 38. Shunted across the field winding 36 are theelectrodes 39 and 40 of the vacuum tube 41 in such a manner that theelectrode 39 is positive with respect to the electrode 40. Shuntedacross the terminals of the machine is a high resistance 43 to anintermediate point of which the grid 44 is connected by tap 45. In thegrid lead is also included a source of voltage 46 which may be poled ineither direction, although it is shown as having its negative endconnected to the grid. The resultant potential of the grid is thealgebraic sum of the potential of source 46 and the I R drop in thatpart of the resistance 43 which is included between tap 45 and cathode40. Since the potential of the grid is determined in part by thepotential drop in resistance 43, it follows that any variation in thevoltage output of the generator will vary the grid potential andconsequently the effective impedance between the anode and cathode ofthe tube, so that the generator may be regulated for constant voltage.Thus if the voltage of the generator would tend to increase, the gridwould become more positive, thereby increasin the space current of thetube and decreasing the field winding current. This change in the fieldwinding current would tend to annul the change in the output voltageacross the leads 37 and 38.

. tions ma Although the use of a battery for determining in part thepotential of the grid of an amplifier is shown only in Fig. 3, it isapparent that the use of such a battery is applicable to any of theother modifications. It is obvious that this invention is not limited inits applications and forms to those above described, but Variousmodificabe made therein as will occur to anyone s illed in the artwithout departing in any wise from the spirit of this invention, asdefined by the appended claims.

What is claimed is:

1. An electric generator having a field winding, and means for holdingsubstantially constant a characteristic of said generator, said meanscomprising a vacuum tube having an anode, a cathode and a controlelectrode a by-path around said field winding comprising said anode andsaid cathode, said anode being connected to the positive terminal ofsaid winding, said cathode being connected to the negative terminal ofsaid winding whereby a portion of the current supplied to said windingis shunted through said tube varying in amount with variations in theeffective impedance of the space current pathbetween said anode and saidcathode, and a resistance in circuit with said generator, and traversedwith current from said generator varying with variations in acharacteristic of said generator, at least a portion of said resistancebeing directly included between said cathode and said control electrodewhereby the potential drop in said resistance controls the potential ofsaid control electrode to produce amplified variations in the efiectiveimpedance between said anode and said cathode.

2. An electric machine having a field winding, current supply leadstherefor, and means for holding substantially constant a characteristicof said machine, said means comprising a vacuum tube having an anode, acathode and a control electrode, a bypath around said winding comprisingsaid anode and said cathode, said anode being connected to the positiveside of said winding, said cathode being connected to the ne tive sideof said winding whereby a portion of the current supplied to saidwinding is shunted through said tube varying in amount with variationsin the efi'ectii e impedance of the space current path between saidanode and said cathode, a resistance in circuit with said means andtraversed by a current varying when variations occur in a characteristicof said machine, at least a portion of said resistance being directlyincluded between said control electrode and said cathode whereby thepotential drop in said resistance controls the potential of said controlelectrode to vary the effective impedance between said anode and saidcathode.

In witness whereof, I hereunto subscribe my name this 27th day of JulyA. D., 1918.

PETER IRVING WOLD.

